The present invention relates to a display device which scans modulated light from a coherent light source according to an image signal and displays an image, and further, to a technology of reducing speckle noise during display.
As illustrated in FIG. 1A, for example, a laser projector has a configuration in which light from laser light emitting elements 10, 11, and 12 of three colors is approximately shaped into parallel light by collimate lenses 20, 21, and 22, reflected by a mirror 50 to be operated, and displays an image on a screen 100. JP-A-2003-021800 discloses a display device with the same configuration. A problem is well-known that in such a display using laser light with a high coherent property, a speckle phenomenon in which speckle patterns are generated at random is caused, and display quality is reduced.
For the purpose of reducing such a speckle phenomenon, examples include a method of mechanically vibrating an optical path as illustrated in WO 2005/078519 A1. However, there is a problem that since a frequency is short to sufficiently reduce speckles, an effect is small.
In addition to a method of operating light, a method of expanding and projecting an image modulated by a light modulation device according to image information is also proposed as illustrated in JP-A-06-208089. In the same manner, speckles are generated as a problem even in this method. With regard to the above, in JP-A-2007-163702, a speckle canceller is proposed in which a liquid crystal is sealed between a pair of transparent substrates.